Rotary drill bits are frequently used to drill oil and gas wells, geothermal wells and water wells. Rotary drill bits may be generally classified as rotary cone or roller cone drill bits and fixed cutter drilling equipment or drag bits. Fixed cutter drill bits or drag bits are often formed with a matrix bit body having cutting elements or inserts disposed at select locations of exterior portions of the matrix bit body. Fluid flow passageways are typically formed in the matrix bit body to allow communication of drilling fluids from associated surface drilling equipment through a drill string or drill pipe attached to the matrix bit body. Such fixed cutter drill bits or drag bits may sometimes be referred to as “matrix drill bits.”
Matrix drill bits are typically formed by placing loose matrix material (sometimes referred to as “matrix powder”) into a mold and infiltrating the matrix material with a binder such as a copper alloy. The mold may be formed by milling a block of material such as graphite to define a mold cavity with features that correspond generally with desired exterior features of the resulting matrix drill bit. Various features of the resulting matrix drill bit such as blades, cutter pockets, and/or fluid flow passageways may be provided by shaping the mold cavity and/or by positioning temporary displacement material within interior portions of the mold cavity. A preformed steel shank or bit blank may be placed within the mold cavity to provide reinforcement for the matrix bit body and to allow attachment of the resulting matrix drill bit with a drill string.
A quantity of matrix material typically in powder form may then be placed within the mold cavity. The matrix material may be infiltrated with a molten metal alloy or binder which will form a matrix bit body after solidification of the binder with the matrix material. Tungsten carbide (WC) powder is often used to form conventional matrix bit bodies.
The methods described herein can advantageously reduce non-desirable cooling of the mold, resulting in improved characteristics of the matrix drill bit. By reducing the energy loss of the mold a further advantage is realized in reducing the energy required from the furnace.
Like reference symbols in the various drawings indicate like elements.